Non‐contrast enhanced simultaneous 3D whole‐heart bright‐blood pulmonary veins visualization and black‐blood quantification of atrial wall thickness

Figures

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  Figure 1. Proposed framework for simultaneous 3D whole‐heart bright‐blood depiction of the PVs and heart anatomy and black‐blood visualization of atrial walls. Two magnetization prepared bright‐blood volumes are acquired in odd and even heartbeats. Specifically, magnetization transfer in combination with an inversion pulse is used in odd heartbeats (MTC‐IR BOOST A), whereas magnetization transfer solely is exploited in even heartbeats (MTC BOOST B), The MTC‐IR acquisition is designed for comprehensive visualization of the heart anatomy. Although a short TI is exploited for fat saturation in odd heartbeats, spectral presaturation (Fat Sat) is used in even heartbeats. Data acquisition is performed using a 3D Cartesian trajectory with spiral profile order and segmented over multiple heartbeats (green, red, blue). A low‐resolution 2D iNAV is acquired in each heartbeat by spatially encoding the ramp‐up pulses of the bSSFP sequences. The bright‐blood MTC‐IR BOOST and MTC BOOST volumes are non‐rigidly motion corrected at the end‐expiratory level and, subsequently, combined in a PSIR‐like reconstruction to generate a complementary black‐blood volume for atrial wall visualization (PSIR BOOST, C).…

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  Figure 2. Image‐navigated respiratory motion tracking with the proposed MT‐prepared BOOST configuration and with a more conventional approach for black‐blood PSIR. The BOOST framework acquires 2 differently weighted bright‐blood data sets (MTC‐IR BOOST and MTC BOOST), providing iNAVs where the heart is depicted with high signal and contrast (A and B). As such, the respiratory displacement can be extracted using a template positioned at the level of the heart itself (red rectangles). This leads to a sharp depiction of the cardiac anatomy after non‐rigid motion correction. Similarly, this results in good anatomy depiction after PSIR computation (E). In contrast, and with a more conventional black‐blood PSIR sequence, iNAVs exhibit low signal and contrast because of blood signal nulling (C) and to a low flip‐angle acquisition for the reference image (D). Consequently, the respiratory motion appears to be tracked at the level of the high‐contrast interface between the liver and the heart and lungs. Although this leads to a sharp delineation of the liver and abdominal vessels, the low signal in both odd and even heartbeats prevents the estimation of non‐rigid motion fields at the level of the…

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  Figure 3. Motion correction performances using 2D translational and 3D non‐rigid motion correction in 2 representative healthy subjects. Before motion correction (red rectangle, A and D), images are affected by severe motion blurring preventing a sharp visualization of the overall cardiac anatomy. Translational motion correction (blue rectangles, B and E) already improves the depiction of several anatomical details, especially in the area where the iNAV template is typically placed (green arrows). Differently, static structures or structures without the template suffer from introduced blurring (yellow arrows). The use of non‐rigid respiratory motion correction successfully restores overall image sharpness, leading to the visualization of the overall cardiac anatomy with excellent image quality (purple rectangles, C and F)

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  Figure 4. Arterial and venous systems visualization with MTC‐IR BOOST and with T2Prep‐IR BOOST in 2 representative healthy subjects. The proposed MTC‐IR BOOST approach provides comparable signal intensity for both arterial and venous blood (A, B, E, and F). As a result, the pulmonary veins (red arrow), arteries (yellow arrows), CS (green arrows), and both coronary arteries and veins (blue arrows) are depicted with high contrast. In contrast, the use of T2Prep in T2Prep‐IR BOOST has a detrimental effect on the venous blood signal (C, D, G, and H). Although the coronary arteries appear sharply depicted (blue plain arrows), the pulmonary veins (red arrows), the CS (green arrows) and the coronary veins (blue dotted arrows) are visualized with reduced signal and contrast. CS, coronary sinus; LAD, left anterior descending coronary artery; AIV, anterior interventricular vein; MTC, magnetization transfer contrast; IR, inversion recovery pulse; T2Prep, T2‐preparation

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  Figure 5. Images obtained in patients presenting with AF and scheduled for an ablation procedure. The contrast‐enhanced clinical sequence is displayed as a maximum intensity projection image in (A), (D), and (G). Non‐contrast enhanced BOOST images are displayed as reformats in (B), (E), and (H) (bright‐blood) and in (C), (F), and (I) (black‐blood). Corresponding anatomical structures at the level of the PVs can be visualized in both images (colored arrows). PV, pulmonary veins

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  Figure 6. Atrial wall segmentation computed in the PSIR BOOST data set obtained with the proposed MT‐prepared BOOST configuration in 3 representative healthy subjects. Segmentation results (red lines) are displayed along the coronal (A, D, and G), transversal (B, E, and H), and sagittal views (C, F, and I). The myocardium, atrial, and ventricular walls are depicted with high contrast in comparison to both blood and surrounding lungs. This allows the segmentation algorithm to successfully discriminate between the 3 different tissues and to successfully track anatomical borders

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  Figure 7. Comparison of atrial wall visualization and segmentation with the proposed MT‐prepared BOOST sequence and with the previously introduced T2‐prepared BOOST configuration. In the bright‐blood MTC‐IR volume (A), designed for the visualization of arterial and venous system (the red arrow indicates one of the pulmonary veins), myocardium and walls exhibit a signal intensity that is intermediate between the one of the blood and that of the lungs (purple arrow). Therefore, intermediate signal intensity of myocardium and walls is preserved in the derived PSIR reconstruction (B); this leads to successful segmentation of myocardium and walls (C, red lines and zoomed areas in blue and yellow boxes). Conversely, in the bright blood T2‐Prep volume (D), venous vessels are not visible (purple arrow) and the myocardial signal is pronouncedly suppressed (red arrow). Consequently, the derived black‐blood PSIR image exhibits reduced contrast between the myocardium and/or walls and the surrounding lungs (E). Although the high‐contrast interface between the blood and the myocardium is successfully recognized and tracked, the segmentation algorithm fails in discriminating between the myocardium and/or…